The present invention relates to a memory device such as a hard disk drive unit or a flash memory card, and more particularly to an invention effectively applied to a technique for prereading storage information of a storage medium such as a nonvolatile memory to a buffer memory.
In a memory device comprising a controller, a buffer memory, a storage medium, and the like, upon arrival of a read request from a host device, the controller reads the data expected to be used later from the storage medium before the read request arrives, and stores it in the buffer memory. This technique is called a preread technique. For example, a hard disk drive (HDD) unit described in Patent Publication 1 has a disk cache and caches expected data to the disk cache in advance to minimize slow access to a magnetic disk. A hard disk controller prereads part of data stored in the magnetic disk and saves it to the disk cache.
[Patent Publication 1]
Japanese Unexamined Patent Publication No. 2001-125829 (sections 24 to 27)